When we see records being broken and unprecedented events such as this, the onus is on those who deny any connection to climate change to prove their case. Global warming has fundamentally altered the background conditions that give rise to all weather. In the strictest sense, all weather is now connected to climate change. Kevin Trenberth

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Friday, October 25, 2013

A team of scientists in Italy believe they have found the molecular
mechanism through which neonicotinoid pesticides adversely impacts the
immune system of honey bees.
The team’s experiments suggest that exposure to neonicotinoids results
in increased levels of a particular protein in bees that inhibits a key
molecule involved in the immune response, making the insects more
susceptible to attack by harmful viruses.

Though previous studies have
indicated that exposure to minute amount of neurotoxic pesticides like
neonicotinoids severely impair the immune systems of bees, making them
more susceptible to pathogens, the underlying mechanism has was not yet
been fully understood. The study, published in the Proceedings of the National Academy of Sciences of the United States of America, is the latest of severalstudies to add weight to the urgency of repeated calls from U.S. beekeeper and environmental groups for the U.S. Environmental Protection Agency (EPA) to suspend the use of neonicotinoid pesticides, as the European Commission decided this past April.Neonicotinoids, a class of insecticides that includes clothianidin and imidicloprid,
are taken up by a plant’s vascular system and expressed through pollen,
nectar and gutation droplets from which bees forage and drink. They are
particularly dangerous because—in addition to being acutely toxic in
high doses—they also result in serious sublethal effects when insects
are exposed to chronic low doses, as they are through pollen and water
droplets laced with the chemical, and dust that is released into the air
when coated seeds are planted with automated vacuum seed planters.
These effects cause significant problems for the health of individual
honey bees as well as the overall health of honey bee colonies. Effects
include disruptions in bee mobility, navigation, feeding behavior,
foraging activity, memory and learning, and overall hive activity.Up until now, the causal link between insecticide exposure and immune
alteration has been unclear. Francesco Pennacchio, Ph.D. of the
University of Naples Federico II, and his colleagues identified a gene
in insects similar to that found in other animals that is known to
regulate the immune response. This gene codes for a leucine-rich repeat
protein family (LRR) which has been shown to suppress the activity of a
key protein involved in immune signaling, called NF-κB. When the
researchers exposed bees to sublethal doses of the neonicotinoid
clothianidin, they saw a significant increase in the expression of the
gene encoding the LRR protein, and a concomitant suppression of the
NF-κB signaling pathway. These effects were not seen when bees were
exposed to the organophosphate insecticide chlorpyriphos.The team infected bees with a common pathogen, deformed wing virus
(DWV), and exposed them to clothianidin and another neonicotinoid,
imidacloprid, at concentrations similar to those that would be found in
the field. The researchers found significantly increased replication of
the virus, which was not seen either in untreated bees or those exposed
to chlorpyriphos.

While the virus is common in bees and usually remains
inactive, it is kept in check by the bees’ immune system. The data
demonstrates that the two neonicotinoids actively promote DWV
replication.“The reported effect on immunity exerted by neonicotinoids will allow
additional toxicological tests to be defined to assess if chronic
exposure of bees to sub-lethal doses of agrochemicals can adversely
affect their immune system and health conditions,” says team member
Francesco Nazzi, Ph.D., of the University of Udine.“Moreover, our data indicates the possible occurrence in insects, as
in vertebrates, of a neural modulation of the immune response,”
continued Nazzi. “This sets the stage for future studies in this
research area, and poses the question on how neurotoxic substances may
affect the immune response.”Since 2006, honey bees nationwide have suffered ongoing and rapid population declines,
from hive abandonment and bee die-off in a phenomenon known as colony
collapse disorder (CCD). These findings add a significant piece of
information to the ongoing and discussion of the role of neonicotinoid
pesticides’ link to CCD, and, according to researchers, this work has
important implications for toxicology and risk assessment studies.The scientists conclude:

The results we report clearly indicate
the need for longer-term toxicity tests, aiming at assessing how the
pathogen progression in honey bees is influenced by insecticide residues
and by their cumulative effects, both on adults and larvae. A
comprehensive and thorough assessment of insecticide impact on bees will
significantly contribute to their conservation and to the development
of more sustainable protocols of intensive agriculture.